1. Field of the Invention
The present invention relates in general to an audio/video signals input terminal circuit for a television or a video cassette recorder, and more particularly to an audio/video signals input terminal circuit with an automatic switching function, wherein audio and video signals from a signal source are automatically inputted to corresponding audio and video signals processing circuits, respectively, when the audio and video signals are indiscriminately inputted through certain input terminals, so that there can be prevented a malfunction due to an erroneous signal input.
2. Description of the Prior Art
Referring to FIG. 1, there is shown a block diagram of a conventional audio/video signals input terminal circuit. As shown in this drawing, the conventional audio/video signals input terminal circuit comprises an input terminal section 1 having three input terminals A, B and C connected, respectively, to a video signal processing circuit 2 and right and left audio signals processing circuits 3 and 4. A video signal Vi from an external signal source is inputted to the video signal processing circuit 2 through the input terminal section 1. Right and left audio signals A.sub.R and A.sub.L from the external signal source are inputted to the right and left audio signals processing circuits 3 and 4 through the input terminal section 1, respectively. The processed video signal Vi from the video signal processing circuit 2 is applied to a cathode ray tube (CRT) and the processed stereo audio signals A.sub.R and A.sub.L from the right and left audio signals processing circuits 3 and 4 are applied to right and left speakers, respectively. As a result, a viewer can listen to a stereo sound as well as watch a video picture.
However, the three input terminals A, B and C in the input terminal section 1 are specified as a video signal input terminal for inputting the video signal Vi, a right audio signal input terminal for inputting the right audio signal A.sub.R and a left audio signal input terminal for inputting the left audio signal A.sub.L, respectively. Also, the right and left audio signals processing circuits 3 and 4 are of the same construction, but are specified to apply their output signals to the right and left speakers, respectively. As a result, in the conventional audio/video signals input terminal circuit with the above-mentioned construction, the video signal Vi must be inputted to the video signal input terminal A connected to the video signal processing circuit 2, the right audio signal A.sub.R must be inputted to the right audio signal input terminal B connected to the right audio signal processing circuit 3 and the left audio signal A.sub.L must be inputted to the left audio signal input terminal C connected to the left audio signal processing circuit 4. Provided that the video signal Vi and the right and left audio signals A.sub.R and A.sub.L are not inputted to the corresponding specified input terminals A, B and C, the signal processing circuits 2, 3 and 4 do not perform normal signal processes, thereby causing the user not to watch a normal video picture and not to listen to a normal stereo sound.
For this reason, external audio and video jacks must accurately be connected to the corresponding input terminals A, B and C in the input terminal section 1 for the normal signal processes in the signal processing circuits 2, 3 and 4, resulting in an inconvenience in use. Also, in erroneous connections, there is no output of the audio and video signals. In this case, the user may misjudge the erroneous connections as a malfunction of the equipment. Although the erroneous connections have been recognized by the user, re-connections are required resulting in an inconvenience. Furthermore, in case where the signal source is far apart from the equipment, audio and video signal lines must be identified one by one for connections to the corresponding input terminals. This results in a further inconvenience.